Advertisements
Advertisements
Question
An electric motor pump is 60% efficient and is rated 2.5 H.P. Calculate the maximum load it can lift through a height of 10m in 8 sec. (1 H.P. = 750 W).
Solution
Useful power supplied by the motor =`(2.5xx750 xx60)/100` watt
= 1125 watt
If maximum load lifted is W kg, then :
Work done in lifting up the load = W × 10 × 10 J
And Work done by the pump = 1125 × 8
Or Load lifted; W =`(1125xx8)/(10xx10)` = 90 kg.
APPEARS IN
RELATED QUESTIONS
What is the work done by the moon when it revolves around the earth?
Express joule in terms of erg.
If the work done by a force in moving an object through a distance of 20 cm is 24.2 J, what is the magnitude of the force?
In which of the following case the work done by a force will be maximum : when the angle between the direction of force and direction of motion is 0° or 90°?
Each of the following statement describes a force acting. Which force is causing work to be done?
How many watts equal one horse power?
Why is the work done on an object moving with uniform circular motion zero?
What is the SI unit of work?
Fill in the boxe to show the corresponding energy transformation.
State the energy changes which take place when A stone dropped from the top of a cliff reaches the ground after some time.
What do you understand by the term energy? Is energy a scalar or vector? How is the energy possessed by a body measured?
A truck driver can load oil drums into the back of the truck by pushing them up a sloping plank, or by lifting them directly. Each drum has a mass of 80 kg, the plank is 3 m long, and the back of the truck is 0.8 m above the ground.
(i) How much force would be needed to lift a drum into the truck directly/without using the plank? (Take g = 10 m/s2)
(ii) How much energy would be required in lifting the drum into the truck without the plank?
(iii) If the force needed to push the drum up the plank is 300 N, why is this less than the answer to part (i)?
(iv) When the truck is loaded, the driver drives off. List the major energy changes that take place in moving the truck.
(v) The driver has to stop at the factory gates. What happens to the kinetic energy of the truck?
A coolie is pushing a box weighing 1500 N up an inclined plane 7.5 m long on to a platform, 2.5 m above the ground.
(i) Calculate the mechanical advantage of the inclined plane. (ii) Calculate the effort applied by the coolie.
(iii) In actual practice, the coolie needs to apply more effort than what is calculated. Give one reason why you think the coolie needs to apply more effort.
What is power? How do you differentiate kilowatt from kilowatt-hour? The Jog Falls in Karnataka state are nearly 20 m high. 2000 tonnes of waterfalls from it in a minute. Calculate the equivalent power if all this energy can be utilized? (g = 10 m s–2)
